The present invention relates to a technology which is effectively applied to a network designing device or a network designing method for supporting optimizing design of an optical communication network.
There is a demand for a technology which enables use of various multimedia services at any time or place. As one of such technologies, a photonic network technology is available, which enables high-speed and inexpensive communication of a large amount of information. Among photonic network technologies, there have been developed a Wavelength Division Multiplexing (WDM) technology which multiplexes and communicates a plurality of optical signals different from one another in wavelength through one optical fiber, and a photonic node technology which constructs a network by regarding each wavelength as one communication path. The development of such technologies has brought about a need to realize a communication network system (hereinafter called communication network) which minimizes equipment introduction expenses (equipment costs) while maintaining high reliability for signal reachability.
The communication network is constituted by using a linear repeater (1R), a regeneration repeater (regenerator, 3R), an Optical Add/Drop Multiplexer (OADM), and the like. Each device is arranged in a predetermined building.
The linear repeater amplifies a signal which it has received by a predetermined gain to compensate for signal attenuation. In the linear repeater, noise mixed in a main signal may be amplified with the main signal by signal amplification. Consequently, in the linear repeater, a signal-to-noise ratio (SN ratio) may be deteriorated to disable regeneration on a reception side.
The regeneration repeater includes a regenerator. The regeneration repeater first divides a multiple signal which it has received among channels. Next, the regeneration repeater executes light-to-electricity conversion for each channel by the regenerator, and executes signal regeneration, regenerated signal amplification, and electricity-to-light conversion. In the regeneration repeater, the deterioration of the SN ratio is prevented since the signal regeneration is executed. The regeneration repeater is more expensive than the linear repeater. Accordingly, it is possible to reduce equipment costs by decreasing the number of regeneration repeaters in the network designing.
The OADM separates a wavelength channel to be terminated as a client signal from the wavelength-multiplexed optical signal. Additionally, the OADM adds a wavelength channel requested to be transmitted by a client side as a part of the wavelength-multiplexed signal. At this time, signal regeneration and regenerated signal amplification by the regenerator are executed when necessary. When the number of routes of a wavelength multiplexing transmission line fiber pair connected to the repeater exceeds two, the OADM may be referred to as a HUB, a multipath OADM, a WXC, or the like.
The HUB converts a signal received by a building in which there is a traffic demand into a client signal. Additionally, the HUB branches a path into a proper route. The HUB may include a regenerator for each channel. When necessary, the HUB executes signal regeneration or regenerated signal amplification by the regenerator. A regenerator needs not be always disposed for each channel of the HUB. Accordingly, it is possible to reduce equipment costs by decreasing the number of regenerators disposed for the channels.
Next, a conventional network designing method will be specifically described. Non-Patent document 1 describes a conventional designing method of a communication network. In the Non-Patent document 1, first, HUB's are installed in all buildings in which there are traffic demands. The HUB includes regenerators for all the channels to execute signal regeneration and regenerated signal amplification. Next, a strength loss only of a multiplexed signal is checked. Based on a result of the check, a linear repeater and a regeneration repeater are installed between the buildings. Then, through a network in which signal reachability is guaranteed among all the buildings, shortest-distance path routing is executed. In the Non-Patent document 1, network resources such as a band and the number of wavelengths are efficiently used by such a method.
As another example of a conventional designing method, there is a technology described in Patent document 1. According to the technology, regarding a communication network which has a meshed geometrical shape, by checking a signal quality for each optical path, a highly efficient communication network system is designed by decreasing redundant regenerators in the HUB. FIGS. 14 to 16 show a basic principle of a conventional network designing method. FIG. 14 is a diagram showing an example of a main function block of a conventional communication network designing device P1. FIG. 15 is a diagram showing an example of a model of a conventional communication network. FIG. 16 is a diagram showing an arrangement example of regenerators in a conventional HUB. In FIG. 16, the regenerator is mounted for each channel in the HUB. FIG. 17 is a flowchart showing a designing process by the conventional communication network designing device P1.
To begin with, topology information, traffic demand information, signal performance information, or the like is input to the communication network designing device P1 (SP1) Next, a section dividing section P2 routes a shortest-distance path, and allocates a proper wavelength based on used link (SP2). In the case of the communication network shown in FIG. 15, the section dividing section P2 assumes that there are 1-channel traffic demands between terminal nodes P5 and P13 and between terminal nodes P5 and P15, and sets a path according to the assumption. Next, the section dividing section P2 arranges devices which terminate all the channels at nodes of a linear degree 1 or 3, i.e., a terminal node and a branch node (SP3). Specifically, the section dividing section P2 arranges terminal devices at the terminal nodes P5, P13 and P15, and arranges regenerators for all the channels of the HUB at a branch node P9. By this process, the communication network to be processed is divided into linear sections in which the node of the linear degree 1 or 3 is a terminal building (referred to as “linear sections”, hereinafter) (SP4). In the case of FIG. 15, the communication network is divided into 3 sections, i.e., the terminal node P5 and the branch node P9 (first linear section), the terminal node P13 and the branch node P9 (second linear section), and the terminal node P15 and the branch node P9 (third linear section).
Next, a section designing section P3 efficiently arranges a linear repeater and a regeneration repeater in each divided linear section by using a conventional technology (SP5). Subsequently, the section designing section P3 combines the divided sections. Next, a regenerator arrangement changing section P4 calculates an accumulated value of signal-to-noise ratios in the buildings for each path. Then, the regenerator arrangement changing section P4 removes regenerators from a section before a regenerator in which the accumulated value becomes maximum which does not exceed a prescribed value (SP6, SP7). In the case of FIG. 15, the regenerator arrangement changing section P4 checks signal performance between the terminal nodes P5 and P13 and between the terminal nodes P5 and P15 for each path, and removes a redundant regenerator from the branch node P9. Then, the communication network designing device P1 creates and outputs a list of components for the device arranged at each node (SP9). As a result, as shown in FIG. 16, the HUB at the branch node P9 is constituted in such a manner that a regenerator is implemented for a partial channel. Thus, equipment introduction expenses are reduced by an amount equivalent to the cost of the regenerators removed.
[Patent Document 1]
Japanese Patent Application Laid-Open Publication No. 2004-048477
[Non-Patent Document 1]
P. Arijs, B. Van Caenegem, P. Demeester, P. Lagasse, W. Van Parys and P. Achten, “Design of ring and mesh based WDM transport networks,” Optical Networks Magazine, Vol. 1, No. 3, pp. 25-40, Jul. 2000.